The present invention relates to a liquid filling apparatus for filling a liquid into containers in a specified amount in each container.
Apparatus of the type mentioned are already known which comprises an apparatus body having a liquid channel connected at one end thereof to a liquid tank and at the other end thereof to a filling nozzle, a metering cylinder provided in the channel between opposite ends thereof in communication with the ends for causing the liquid to be filled to flow into and out of the liquid channel by strokes of a piston housed in the cylinder, and a check valve disposed upstream from the metering cylinder of the liquid channel. The check valve is forced open by a negative pressure produced within the metering cylinder by the inflow stroke of the piston.
The liquids to be filled include those which contain a gas as it is or as dissolved in the liquid and are liable to release bubbles. Such liquids are, for example, a liquid which needs to be filled hot, a liquid which has not been treated for deaeration before feeding to the filling apparatus, and a liquid which is liable to alter in properties due to a pressure change. When subjected to a negative pressure produced within the metering cylinder, such a liquid releases bubbles. If the bubbles produced remain and collect within the metering cylinder, the amount of liquid to be filled decreases with time.
The decrease in the amount of liquid to be filled can be prevented by discharging the bubbles from the metering cylinder every stroke of the piston. For this purpose, it is conventional practice to produce turbulence within the metering cylinder by ingeniously shaping the cylinder, cause the bubbles produced in the cylinder to flow out of the cylinder along with the liquid to be filled and fill the outflow into a container. However, if the bubbles are placed into the container along with the liquid, the liquid is liable to bubble up or scatter to result in a lower filling capacity.
An object of the present invention is to prevent formation of bubbles within the metering cylinder and to provide a liquid filling apparatus which is free of the problems due to the occurrence of bubbles and a method of using the apparatus.
The present invention provides a liquid filling apparatus comprising an apparatus body having a liquid channel connected at one end thereof to a liquid tank and at the other end thereof to a filling nozzle, a metering cylinder provided in the liquid channel between opposite ends thereof in communication with the ends for causing the liquid to be filled to flow into and out of the liquid channel by strokes of a piston housed in the cylinder, and a check valve disposed upstream from the metering cylinder of the liquid channel, the liquid filling apparatus being characterized in that the apparatus comprises valve opening-closing means for mechanically operating the check valve so as to open the valve during the inflow stroke of the piston and to close the valve during the outflow stroke of the piston.
The liquid filling apparatus of the invention has valve opening-closing means for mechanically operating the check valve so as to open the valve during the inflow stroke of the piston and to close the valve during the outflow stroke of the piston. Accordingly, no negative pressure is produced within the metering cylinder by the inflow stroke of the piston, with the result that the liquid to be filled is prevented from releasing bubbles. The absence of bubbles entails the following advantages. First, the amount of liquid to be filled is stabilized. Second, the liquid can be filled in a satisfactory state, permitting a high-speed filling operation. Third, even if the liquid is deaerated insufficiently when to be fed to the filling apparatus, the liquid can be filled satisfactorily to improve the freedom of the plant equipment. Fourth, with no limitations imposed on the capacity or shape of the metering cylinder, the filling apparatus can be designed with greater freedom.
Preferably, the liquid filling apparatus comprises means for setting the check valve at large and small two degrees of opening.
According to an embodiment of the invention, the liquid filling apparatus further comprises a valve seat facing downstream with respect to the direction of flow of the liquid and provided on a peripheral wall defining the liquid channel at a portion thereof upstream from the metering cylinder; the check valve comprising a valve disk movable toward and away from the valve seat on the downstream side thereof with respect to the flow direction, and a spring for biasing the valve disk toward the valve seat; the valve opening-closing means comprising a fluid pressure cylinder having a piston rod and so disposed as to move the valve disk away from the valve seat by an advancing stroke of the piston rod; the setting means comprising a movable engaging member engageable with and disengageable from the piston rod, and an actuator for moving the engaging member so that the disengagement of the member from the piston rod and the engagement of the member with the piston rod correspond respectively to the large and small degrees of opening of the check valve. The check valve can then be set easily at the large degree of opening or alternatively at the small degree.
The engaging member may be so disposed as to be movable straight across the path of movement of the piston rod, the actuator being a fluid pressure cylinder having a piston rod connected to the engaging member.
The liquid filling apparatus may further be so adapted that the interior of the liquid channel is cleaned or deaerated with the check valve set at the large degree of opening, and that the check valve is set at the small degree of opening for the filling operation. The liquid channel can then be cleaned or deaerated rapidly, smoothly and efficiently, while the outflow and inflow strokes of the piston can be readily timed with the opening and closing of the check valve.